Firing control devices and day-time/night-time sighting optical devices attached to rifles, machine guns or crew-served weapons generally use one or more of day-time optical devices, thermal imaging optical devices and laser optical devices for detecting objects. For the maximum performance of detecting objects, however, there has been need for a composite optical device incorporating the laser optical device as well as the day-time optical device and thermal-imaging optical device. Also it has been needed a separate displaying device for displaying the state of the devices, texts and sighting point.
Although some devices have included all these functions in them, the devices had the problem of being large in size and heavy in weight, making it difficult for a user to carry and use the device.
Also, it is hard to recognize texts or images displayed on the display panel when the optical device is used at day time or when the display is illuminated by bright light such as sun light, vehicle head lamp or illuminating shell. Therefore, most conventional optical devices use an aperture for controlling the amount of incoming light. However, it is difficult to control the amount of lights to a uniform distribution using an aperture, and there is much difficulty in controlling various optical devices inside a composite optical device incorporating them from outside. Also, conventional devices are not appropriate for use in military equipments or in special devices which should be operated under conditions of various temperatures (especially bad operability at low temperature) or physical impacts. Although some polarizer is used to control the amount of light in military devices, they have been used in each optical device (day-time or thermal-imaging optical device and laser device) respectively and appropriate structure for a composite optical device still needs to be invented.